ads1115rpi.cpp

#include "ads1115rpi.h"

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>


void ADS1115rpi::start(ADS1115settings settings) {
	ads1115settings = settings;

	char gpioFilename[20];
	snprintf(gpioFilename, 19, "/dev/i2c-%d", settings.i2c_bus);
	fd_i2c = open(gpioFilename, O_RDWR);
	if (fd_i2c < 0) {
	    char i2copen[] = "Could not open I2C.\n";
#ifdef DEBUG
	    fprintf(stderr,i2open);
#endif
	    throw i2copen;
	}
	
	if (ioctl(fd_i2c, I2C_SLAVE, settings.address) < 0) {
	    char i2cslave[] = "Could not access I2C adress.\n";
#ifdef DEBUG
	    fprintf(stderr,i2cslave);
#endif
	    throw i2cslave;
	}
	
#ifdef DEBUG
	fprintf(stderr,"Init.\n");
#endif
	// Enable RDY
	i2c_writeWord(reg_lo_thres, 0x0000);
	i2c_writeWord(reg_hi_thres, 0x8000);

	unsigned r = (0b10000000 << 8); // kick it all off
	r = r | (1 << 2) | (1 << 3); // data ready active high & latching
	r = r | (settings.samplingRate << 5);
	r = r | (settings.pgaGain << 9);
	r = r | (settings.channel << 12) | 1 << 14; // unipolar
	i2c_writeWord(reg_config,r);

#ifdef DEBUG
	fprintf(stderr,"Receiving data.\n");
#endif

	chipDRDY = gpiod_chip_open_by_number(settings.drdy_chip);
	pinDRDY = gpiod_chip_get_line(chipDRDY,settings.drdy_gpio);

	int ret = gpiod_line_request_rising_edge_events(pinDRDY, "Consumer");
	if (ret < 0) {
#ifdef DEBUG
	    fprintf(stderr,"Request event notification failed on pin %d and chip %d.\n",settings.drdy_chip,settings.drdy_gpio);
#endif
	    throw "Could not request event for IRQ.";
	}

	running = true;

	thr = std::thread(&ADS1115rpi::worker,this);
}


void ADS1115rpi::setChannel(ADS1115settings::Input channel) {
	unsigned r = i2c_readWord(reg_config);
	r = r & (~(3 << 12));
	r = r | (channel << 12);
	i2c_writeWord(reg_config,r);
	ads1115settings.channel = channel;	
}


void ADS1115rpi::dataReady() {
	float v = (float)i2c_readConversion() / (float)0x7fff * fullScaleVoltage() * 2;
	for(auto &cb: adsCallbackInterfaces) {
	    cb->hasADS1115Sample(v);
	}
}


void ADS1115rpi::worker() {
    while (running) {
	const struct timespec ts = { 1, 0 };
	gpiod_line_event_wait(pinDRDY, &ts);
	struct gpiod_line_event event;
	gpiod_line_event_read(pinDRDY, &event);
	dataReady();
    }
}


void ADS1115rpi::stop() {
    if (!running) return;
    running = false;
    thr.join();
    gpiod_line_release(pinDRDY);
    gpiod_chip_close(chipDRDY);
    close(fd_i2c);
}


// i2c read and write protocols
void ADS1115rpi::i2c_writeWord(uint8_t reg, unsigned data)
{
	uint8_t tmp[3];
	tmp[0] = reg;
	tmp[1] = (char)((data & 0xff00) >> 8);
	tmp[2] = (char)(data & 0x00ff);
	long int r = write(fd_i2c,&tmp,3);
        if (r < 0) {
#ifdef DEBUG
                fprintf(stderr,"Could not write word from %02x. ret=%d.\n",ads1115settings.address,r);
#endif
                throw "Could not write to i2c.";
        }
}

unsigned ADS1115rpi::i2c_readWord(uint8_t reg)
{
	uint8_t tmp[2];
	tmp[0] = reg;
	write(fd_i2c,&tmp,1);
        long int r = read(fd_i2c, tmp, 2);
        if (r < 0) {
#ifdef DEBUG
                fprintf(stderr,"Could not read word from %02x. ret=%d.\n",ads1115settings.address,r);
#endif
                throw "Could not read from i2c.";
        }
        return (((unsigned)(tmp[0])) << 8) | ((unsigned)(tmp[1]));
}

int ADS1115rpi::i2c_readConversion()
{
	const int reg = 0;
	char tmp[3];
	tmp[0] = reg;
	write(fd_i2c,&tmp,1);
        long int r = read(fd_i2c, tmp, 2);
        if (r < 0) {
#ifdef DEBUG
                fprintf(stderr,"Could not read ADC value. ret=%d.\n",r);
#endif
                throw "Could not read from i2c.";
        }
        return ((int)(tmp[0]) << 8) | (int)(tmp[1]);
}